[Pw_forum] fixed spin moment calculation

[yumin qian]

thanks for your reply ,I  changed the lambda=5.0 and used
   occupations='tetrahedra'  but the magnetization still did not converge to
the initial value ,but the total energy converged.
I do not know what is the problem.


> 2009/3/11 Gabriele Sclauzero <sclauzer at sissa.it>
>
>
>>
>> yumin qian wrote:
>> >   Dear PWSCF users
>> >    I am doing calculate on the antiferromagnetic ground state of
>> > LiNiO2, I want to plot the energy as a function of fixed spin moment  of
>> > Ni atom.
>> >   the following is my in put file for pwscf
>> >
>> >  &system
>> >     ibrav = 0, nat=16 , ntyp= 4,
>> >     ecutwfc = 35.0, ecutrho = 200.0,
>> >     occupations='smearing', smearing='gaussian', degauss=0.02
>>
>> First of all a word of caution: this value of degauss may not be low
>> enough to converge
>> the magnetization (even if it is more than enough to converge the total
>> energy). Also
>> ecutrho may not be high enough to converge total energy, since you're
>> using US PPs.
>>
>> >     nspin=2,constrained_magnetization='atomic',
>> > starting_magnetization(1)= 0.0,
>> > starting_magnetization(2)= 1.8,
>> > starting_magnetization(3)=-1.8,
>> > starting_magnetization(4)= 0.0,
>> > lda_plus_u=.true.
>> > Hubbard_U(1)=0.0
>> > Hubbard_U(2)=3.0
>> > Hubbard_U(3)=3.0
>> > Hubbard_U(4)=0.0
>> >   /
>> >  &electrons
>> >     diagonalization='david',
>> >     conv_thr = 1.0e-6,
>> >     mixing_beta = 0.5,
>> >  /
>> > ATOMIC_SPECIES
>> > Li     *6.914*      Li.pbe-n-mt_bw.UPF
>> > Ni1   *58.6934*    Ni.pbe-n-van.UPF
>> > Ni2   *58.6934*    Ni.pbe-n-van.UPF
>> > O   15.9994      O.pbe-van_bm.UPF
>> >
>> > and the output file gives
>> >
>> >
>>  ==============================================================================
>> >      atom number    5 relative position :   -0.1652   0.2839   0.5083
>> >      charge :     2.373353
>> >      magnetization :          1.544423
>> >      magnetization/charge:    0.650735
>> >      constrained moment :     1.800000
>> >
>> >
>>  ==============================================================================
>> > the output file gives a magnetic moment of 1.5444 ,how should I do to
>> > make the calculation  converge to the starting_magnetization 1.8 ?
>>
>> You can increase the lambda parameter which premultiplies the penalty
>> energy added in
>> v_of_rho. In the limit your constraint gets satisfied, the energy should
>> not depend on
>> which lambda you chose, but you may want to verify this.
>> The default should be 1. I think is not enough to force the magnetization
>> on the atom.
>>
>> However, I think that the magnetization of a single atom inside a bulk
>> material or in
>> general when it forms covalent bonds is not a well defined quantity, so I
>> would not care
>> too much of the precise number I get for the magnetization, since it may
>> well change if I
>> change which portion of charge is attributed to which atom (remember that
>> you're using a
>> plane waves code, and PWs do not know anything about atomic orbitals a
>> priori...)
>>
>> HTH
>>
>> GS
>>
>> >
>> > I change the starting_magnetization(2) and starting_magnetization(3)
>> > from 1.8 to 0.8 , then I will get the E(m) curve.  how should I do ,
>> > does anyone give
>> > a suggestion ?
>> > --
>> > Sincerely Y. M. Qian
>> > Lab.of Condensed Matter Theory and Materials Computation
>> > Institute of Physics
>> > Chinese Academy of Sciences
>> > Tel:  + 8610 8264 9147
>> > E-Mail:yuminqian at gmail.com <E-Mail%3Ayuminqian at gmail.com> <mailto:
>> E-Mail%3Ayuminqian at gmail.com <E-Mail%253Ayuminqian at gmail.com>>
>> > P.O.Box 603   Beijing 100190
>> > China
>> >
>> >
>> > ------------------------------------------------------------------------
>> >
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>>
>> --
>>
>>
>> o ------------------------------------------------ o
>> | Gabriele Sclauzero, PhD Student                  |
>> | c/o:   SISSA & CNR-INFM Democritos,              |
>> |        via Beirut 2-4, 34014 Trieste (Italy)     |
>> | email: sclauzer at sissa.it                         |
>> | phone: +39 040 3787 511                          |
>> | skype: gurlonotturno                             |
>> o ------------------------------------------------ o
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>>
>
>
>
> --
> Sincerely Y. M. Qian
> Lab.of Condensed Matter Theory and Materials Computation
> Institute of Physics
> Chinese Academy of Sciences
> Tel:  + 8610 8264 9147
> E-Mail:yuminqian at gmail.com <E-Mail%3Ayuminqian at gmail.com>
>  P.O.Box 603   Beijing 100190
> China
>
>


-- 
Sincerely Y. M. Qian
Lab.of Condensed Matter Theory and Materials Computation
Institute of Physics
Chinese Academy of Sciences
Tel:  + 8610 8264 9147
E-Mail:yuminqian at gmail.com <E-Mail%3Ayuminqian at gmail.com>
P.O.Box 603   Beijing 100190
China
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